The invention relates to a device to clean a printing medium, in that the printing medium is structured such that it carries new image information for each print cycle that is inked with ink material that is printed upon a medium, for example paper or an intermediate carrier. Furthermore, the invention concerns a method to clean a print medium.
Printing methods in which the printing medium is newly structured by a digital method for each print cycle are known from WO 98/32608, WO 97/36746, and U.S. Pat. No. 5,067,404 from the same applicant. For example, the surface of the printing medium is structured in WO 98/32608 such that ink-attracting and ink-repelling regions exist. A substance present in the solid phase, preferably water, is used as an ink-repelling medium generated thereon by cooling the surface of the printing medium. After the ink material is transfer printed to the paper, the surface of the printing medium is cleaned of ink residue. The printing medium is then structured anew and carries new image information. A digital method is used in the structuring, for example using the radiation of a laser, a laser diode, an LED or an LED array. In a method according to WO 97/36746, a thin moisture film is generated every print cycle on the surface of the printing medium by charging the surface with water vapor, and subsequently the structuring of the moisture film is undertaken. The aforementioned documents are herewith included by reference in the disclosure of the present patent application.
Further methods and printing devices to print a medium material and to clean a print roller are known from the PCT patent applications with serial numbers PCT/EP00/06028 and PCT/EP00/06026 by the same applicant. A plurality of depressions are present on the surface of a printing medium for the acceptance of printing fluid. Ink material is placed in these depressions with the aid of an inking station. The printing fluid contained in the depressions is used to print on a printing medium at a transfer printing location. With the aid of a digital method, every print cycle the print fluid in the depressions is dealt with in such a manner that a portion of the print fluid is transfer printed at the transfer printing location, and another portion remains in the depressions. Both of these cited documents are also herewith included by reference in the disclosure of the present patent application.
It is necessary in the cited printing methods that, before applying new image information to the surface of the printing medium, this surface is cleaned of ink residues and other substances. The cleaning process must be of such a nature that it can be included in the printing process without problems, in particular upon consideration of the structuring of the surface of the printing medium with the aid of a digital method. As a result, the cleaning duration must be short, and a large number of cleaning cycles should be possible for the same cleaning medium.
The prior art is further referenced in U.S. Pat. No. 5,067,494 as well as in document DE-A-19 750 242, as given in the preamble.